Father: Vikings RB Peterson takes next step in knee rehab

Minnesota Vikings running back Adrian Peterson is right on schedule in his rehabilitation from a torn anterior cruciate ligament in his left knee, and the next step in his recovery is running.

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That's running ... in a pool.

Peterson tried some light pool running at Vikings headquarters early this week, his father, Nelson, told the St. Paul Pioneer Press. Peterson had targeted Feb. 28 as the date he would begin running, which prompted coach Leslie Frazier to say the four-time Pro Bowl running back needed to "temper his emotions" as he aims to make it back in time for the regular-season opener.

Peterson underwent ACL surgery Dec. 30 -- a little more than eight months before the start of the 2012 season -- and has maintained in recent weeks that his rehab is on track.